Question

If vapours of dry ammonia gas are brought into contact with red litmus paper, what will happen to the colour of the litmus paper?

• A. Litmus paper turns blue
• B. Litmus paper turns pink
• C. No change in the litmus paper
• D. Litmus paper turns yellow

Answer 1

The correct option is C No change in the litmus paper

The colour of the litmus paper will remain unchanged because ammonia $\left({\text{NH}}_3\right)$ gas does not show basic character in the absence of water.

In the presence of water, ammonia gets converted to ammonium ${\text{(NH}}_4^{+})$ ion, which turns red litmus to blue as it is a basic solution.

${NH}_3\left(aq\right)+H_{2}O\left(l\right)\leftrightharpoons N{H}_4^{+}\left(aq\right)+O{H}^{-}\left(aq\right)$